Internal combustion engines suffer from a process called blow-by where combustion gasses leak past the piston rings into the crankcase. To prevent seal damage these gasses will have to be vented, which can be done by a closed circuit breather system (CCB) or an open circuit breather system (OCB). When using an OCB, the gasses flow from the crankcase to the cylinder head and are from there vented to atmosphere. With a CCB, the gasses flow from the crankcase to the cylinder head and are from there re-introduced into the induction system, where they are burned off and subsequently depart the engine via the conventional exhaust system.
A major problem associated with both OCB and CCB systems is that the blow-by gasses usually carry a substantial amount of oil particles caused by reciprocating and rotating elements in the engine. This process is called oil carry-over and can pose several problems:                in certain CCB systems the vented gas is fed through a filter to minimise the amount of carry-over oil in the blow-by gasses, before introduction of the gasses into the intake manifold for combustion. As the filter is an expensive service item, oil carry-over increases operating costs;        in CCB systems without a filter, the oil can cause fouling of components of the induction system such as turbocharger compressor vanes and engine poppet valves. Also, the liquid oil can form deposits on the valves which can be detrimental to the performance of the air intake system;        in OCB systems where the gasses are vented to air, oil carry-over can raise emission levels significantly;        oil carry-over can be a significant cause of oil loss and hence increases operating costs.        
It is known to provide a PCV (Positive Crankcase Ventilation) valve to limit oil carry over. An example of such an apparatus is disclosed in U.S. Pat. No. 5,024,203. However, this design has several undesired characteristics in that it is fitted external to the engine thus enlarging the engine envelope, it requires a controlled heating process of the vapours, and several additional flow paths must be added to the engine to control the flow of the fluids involved. This combination of factors make the design complex, expensive, and introduces significant design constraints for both the engine manufacturer and the customers who wish to incorporate the engine into their products.
The present invention is directed to solving one or more of the problems set forth above.